1. Technical Field
The disclosure relates to an inkjet printer with an ink circulation system configured to circulate ink.
2. Related Art
A general inkjet printer prints images, characters, and the like by ejecting ink from nozzles of inkjet heads to a print sheet.
Among such inkjet printers, there is known an inkjet printer provided with an ink circulation system which constantly circulates the ink in order to remove foreign matters such as dusts mixed in the ink and to uniformly heat the ink.
The ink used in the inkjet printers with the ink circulation system typically has temperature characteristics in which the viscosity changes depending on a temperature condition, i.e., the viscosity is high at low temperature and is low at high temperature. Moreover, depending on the viscosity of the ink, an increase in an amount of mist generated by ejection and variations in diameter of an ink drop and ejection speed may occur, so that a printed object with high definition cannot be obtained in some cases.
Accordingly, the temperature of the ink needs to be adjusted to such a level that the ink can have an appropriate viscosity.
Japanese Unexamined Patent Application Publication No. 2011-213028 proposes an inkjet printer which includes an ink circulation passage where to circulate ink between an upper tank and a lower tank and which controls a total circulation amount of the ink circulating through the ink circulation passage on the basis of liquid levels measured by three liquid level meters provided in each of the upper tank and the lower tank, in order to reduce a time necessary for completion of a warm-up operation (necessary for temperature adjustment of the ink). Specifically, each of the upper tank and the lower tank includes a first upper-limit liquid level detector, a second upper-limit liquid level detector, and a lower-limit liquid level detector as the liquid level meters. The inkjet printer controls the liquid level to a first liquid level by using detection values obtained by the first upper-limit liquid level detector and the lower-limit liquid level detector and controls the liquid level to a second liquid level by using detection values obtained by the second upper-limit liquid level detector and the lower-limit liquid level detector.